1 //===-- AMDGPUAlwaysInlinePass.cpp - Promote Allocas ----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file
10 /// This pass marks all internal functions as always_inline and creates
11 /// duplicates of all other functions and marks the duplicates as always_inline.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "AMDGPU.h"
16 #include "AMDGPUTargetMachine.h"
17 #include "Utils/AMDGPUBaseInfo.h"
18 #include "llvm/CodeGen/CommandFlags.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Support/CommandLine.h"
22
23 using namespace llvm;
24
25 namespace {
26
27 static cl::opt<bool> StressCalls(
28 "amdgpu-stress-function-calls",
29 cl::Hidden,
30 cl::desc("Force all functions to be noinline"),
31 cl::init(false));
32
33 class AMDGPUAlwaysInline : public ModulePass {
34 bool GlobalOpt;
35
36 public:
37 static char ID;
38
AMDGPUAlwaysInline(bool GlobalOpt=false)39 AMDGPUAlwaysInline(bool GlobalOpt = false) :
40 ModulePass(ID), GlobalOpt(GlobalOpt) { }
41 bool runOnModule(Module &M) override;
42
getAnalysisUsage(AnalysisUsage & AU) const43 void getAnalysisUsage(AnalysisUsage &AU) const override {
44 AU.setPreservesAll();
45 }
46 };
47
48 } // End anonymous namespace
49
50 INITIALIZE_PASS(AMDGPUAlwaysInline, "amdgpu-always-inline",
51 "AMDGPU Inline All Functions", false, false)
52
53 char AMDGPUAlwaysInline::ID = 0;
54
55 static void
recursivelyVisitUsers(GlobalValue & GV,SmallPtrSetImpl<Function * > & FuncsToAlwaysInline)56 recursivelyVisitUsers(GlobalValue &GV,
57 SmallPtrSetImpl<Function *> &FuncsToAlwaysInline) {
58 SmallVector<User *, 16> Stack(GV.users());
59
60 SmallPtrSet<const Value *, 8> Visited;
61
62 while (!Stack.empty()) {
63 User *U = Stack.pop_back_val();
64 if (!Visited.insert(U).second)
65 continue;
66
67 if (Instruction *I = dyn_cast<Instruction>(U)) {
68 Function *F = I->getParent()->getParent();
69 if (!AMDGPU::isEntryFunctionCC(F->getCallingConv())) {
70 // FIXME: This is a horrible hack. We should always respect noinline,
71 // and just let us hit the error when we can't handle this.
72 //
73 // Unfortunately, clang adds noinline to all functions at -O0. We have
74 // to override this here until that's fixed.
75 F->removeFnAttr(Attribute::NoInline);
76
77 FuncsToAlwaysInline.insert(F);
78 Stack.push_back(F);
79 }
80
81 // No need to look at further users, but we do need to inline any callers.
82 continue;
83 }
84
85 append_range(Stack, U->users());
86 }
87 }
88
alwaysInlineImpl(Module & M,bool GlobalOpt)89 static bool alwaysInlineImpl(Module &M, bool GlobalOpt) {
90 std::vector<GlobalAlias*> AliasesToRemove;
91
92 SmallPtrSet<Function *, 8> FuncsToAlwaysInline;
93 SmallPtrSet<Function *, 8> FuncsToNoInline;
94 Triple TT(M.getTargetTriple());
95
96 for (GlobalAlias &A : M.aliases()) {
97 if (Function* F = dyn_cast<Function>(A.getAliasee())) {
98 if (TT.getArch() == Triple::amdgcn &&
99 A.getLinkage() != GlobalValue::InternalLinkage)
100 continue;
101 A.replaceAllUsesWith(F);
102 AliasesToRemove.push_back(&A);
103 }
104
105 // FIXME: If the aliasee isn't a function, it's some kind of constant expr
106 // cast that won't be inlined through.
107 }
108
109 if (GlobalOpt) {
110 for (GlobalAlias* A : AliasesToRemove) {
111 A->eraseFromParent();
112 }
113 }
114
115 // Always force inlining of any function that uses an LDS global address. This
116 // is something of a workaround because we don't have a way of supporting LDS
117 // objects defined in functions. LDS is always allocated by a kernel, and it
118 // is difficult to manage LDS usage if a function may be used by multiple
119 // kernels.
120 //
121 // OpenCL doesn't allow declaring LDS in non-kernels, so in practice this
122 // should only appear when IPO passes manages to move LDs defined in a kernel
123 // into a single user function.
124
125 for (GlobalVariable &GV : M.globals()) {
126 // TODO: Region address
127 unsigned AS = GV.getAddressSpace();
128 if ((AS == AMDGPUAS::REGION_ADDRESS) ||
129 (AS == AMDGPUAS::LOCAL_ADDRESS &&
130 (!AMDGPUTargetMachine::EnableLowerModuleLDS || !GV.hasInitializer())))
131 recursivelyVisitUsers(GV, FuncsToAlwaysInline);
132 }
133
134 if (!AMDGPUTargetMachine::EnableFunctionCalls || StressCalls) {
135 auto IncompatAttr
136 = StressCalls ? Attribute::AlwaysInline : Attribute::NoInline;
137
138 for (Function &F : M) {
139 if (!F.isDeclaration() && !F.use_empty() &&
140 !F.hasFnAttribute(IncompatAttr)) {
141 if (StressCalls) {
142 if (!FuncsToAlwaysInline.count(&F))
143 FuncsToNoInline.insert(&F);
144 } else
145 FuncsToAlwaysInline.insert(&F);
146 }
147 }
148 }
149
150 for (Function *F : FuncsToAlwaysInline)
151 F->addFnAttr(Attribute::AlwaysInline);
152
153 for (Function *F : FuncsToNoInline)
154 F->addFnAttr(Attribute::NoInline);
155
156 return !FuncsToAlwaysInline.empty() || !FuncsToNoInline.empty();
157 }
158
runOnModule(Module & M)159 bool AMDGPUAlwaysInline::runOnModule(Module &M) {
160 return alwaysInlineImpl(M, GlobalOpt);
161 }
162
createAMDGPUAlwaysInlinePass(bool GlobalOpt)163 ModulePass *llvm::createAMDGPUAlwaysInlinePass(bool GlobalOpt) {
164 return new AMDGPUAlwaysInline(GlobalOpt);
165 }
166
run(Module & M,ModuleAnalysisManager & AM)167 PreservedAnalyses AMDGPUAlwaysInlinePass::run(Module &M,
168 ModuleAnalysisManager &AM) {
169 alwaysInlineImpl(M, GlobalOpt);
170 return PreservedAnalyses::all();
171 }
172